This study was undertaken to evaluate the in-vitro efficacy of various botanical extracts against leaf spot disease of marigold, caused by Alternaria alternata. A field survey conducted across different locations of Hyderabad District, Sindh, revealed variable levels of disease incidence: Ghangra Mori (35%), Tando Hyder (30%), Rahooki (25%), Moosa Khatyan (20%), and Hosri (15%). The highest disease incidence was recorded at Ghangra Mori, whereas Hosri exhibited the lowest. Among the tested botanicals, neem extract demonstrated the strongest inhibitory effect on the mycelial growth of A. alternata, with colony diameters of 48 mm, 40 mm, and 34 mm at 2%, 4%, and 6% concentrations, respectively. In comparison, datura extract allowed relatively higher fungal growth (75.5 mm, 63 mm, and 57.5 mm at corresponding concentrations). Garlic extract restricted colony growth by 49%, 43%, and 36%, while ginger extract limited growth to 50 mm, 43.5 mm, and 36.5 mm at 2%, 4%, and 6% concentrations, respectively. Overall, the minimum colony growth of A. alternata was recorded at 6% neem extract, followed by garlic, ginger, and datura. These results clearly indicate that neem extract, particularly at higher concentrations, is the most effective botanical treatment for suppressing the in-vitro growth of A. alternata.
Jarwar et al. (2025) studied this question.